The Great Filter is a concept in the field of astrobiology and the Fermi Paradox, which addresses the seeming contradiction between the high probability of extraterrestrial life existing in the universe and the lack of evidence for, or contact with, such civilizations. The Great Filter suggests that at some stage in the evolution of life, there are one or more highly improbable steps, events, or barriers that prevent the emergence of advanced civilizations.

The idea is that if these filters exist, they could be located at various points in the timeline of a planet's evolution, from the emergence of simple life to the development of intelligent, technologically advanced civilizations. Some possibilities for these filters include the development of life itself, the transition from single-celled to multicellular organisms, the emergence of intelligence, the ability to develop advanced technology without destroying oneself, and others.

The implication of the Great Filter concept is that if a civilization manages to successfully navigate all the potential filters, it might be extremely rare in the universe. This could explain why we haven't yet observed any evidence of extraterrestrial civilizations, despite the high probability of their existence according to some estimates. It also raises questions about the future of humanity and our own potential filters as we continue to advance.